Diagnosis Of Cracks Based On Advanced Pso Wavelet Finite Element Method

The appearance of crack usually cause structural damage and lead to catastrophic security acciden,so the early identification of cracks to guarantee the safety of structure is significant in engineering practice.It has many advantages because of using the multi-resolution wavelet basis instead of traditional polynomial interpolation function.One is that it keeps the discrete approximation characteristics of traditional finite element method,which can easily solve the complex bounding conditions.The other is that it posses multi-scale and multi-resolution properties of wavelet which can obtain wavelet element at different scale according to different need,so the parameter identification based on wavelet finite element of a crack in the cantilever beam is mainly discussed in this thesis.The properties of B-spline Wavelet on the Interval(BSWI)are analyzed.The derivatives of sacling functions and wavelet function of B-spline Wavelet on the Interval are calculated.The multiresolution of wavelet is brought in finite element by using scaling function as an interpolation function,then B-spline Wavelet on the Interval based beam element are constructed,and the numerical examples show their high accuracy in beam bending problems and the natural frequency of the intact cantilever beam is calculated using the above method are compared with analytical solution to get good precision.The wavelet finite element analysis of the transverse vibration of a cracked beam is developed based on the massless rotational spring model,and the natural frequencies are solved,whose accordance with the analytical results shows the accuracy of wavelet finite element.Then the importance of detecting the inherent frequency of mechanical structure is analyzed.a method based on the variation mode decomposition was investigated.methods based on variation mode decomposition?modal analysis by ANSYS?empirical mode decomposition?ensemble empirical mode decomposition were applied respectively and the analytic results show that the method based on variation mode decomposition presented here is effective.In the end,based on the problem of traditional wavelet finite element identification,this paper puts forward the diagnosis of the crack by the wavelet finite element method based on the improved particle swarm,and verifies the effectiveness of this method.